Java backend: fixed a bug related to translating Bag node of generic KIL to CellCollection node of java KIL
included the kool-untyped definition modified for the Java backend
Java backend: created class TermCons in the Java backend KIL; implemented related functionalities in visitors, transformers, and unifiers
fixed a StringOutOfBoundsException bug
correctly handled the case that the result configuration of krun is non-ground
Java backend: minor
Java backend: implemented functions which have KLabel as return value; implemented MetaK#getKLabel()
Java backend: properly hooked getKLabel_ and _==KLabel_ to their Java backend implementations
Java backend: fixed a bug that leads to crash introduced in previous commit